The poet and writer has urged political reform. Officials in Beijing say his call for democracy is a threat to the Communist Party.

Reporting from Beijing — The Chinese government has put on trial a prominent civil rights dissident who has already spent more than a year in detention for writing a controversial manifesto calling for political reform.

Liu Xiaobo, a 53-year-old poet, literary critic and former professor previously jailed for nearly two years for his role in the 1989 student-led protests at Tiananmen Square, on Wednesday faced a two-hour hearing that was closed to the public.

Officials claim that Liu's calls for democracy and free speech are a threat to the ruling Communist Party. He faces up to 15 years in prison if convicted on a charge of "incitement to subvert state power." A verdict could come as early as Friday.

A U.S. State Department spokesman described Liu's treatment as "uncharacteristic of a great country."

About a dozen foreign diplomats stood outside the Beijing courthouse after being barred from the proceedings. As plainclothes security officers looked on, activists handed out yellow ribbons signifying their call for Liu's release.

"As far as we can tell, this man's crime was simply signing a piece of paper that aspires to a more open and participatory form of government. That is not a crime," State Department spokesman P.J. Crowley said in Washington, characterizing the trial as a move that will "likely lead to a political conviction."

Chinese activists held on such charges are almost always sentenced to lengthy prison terms.

Activists on Wednesday expressed concern for Liu.

"The case sends a message domestically to the Chinese citizenry and intellectuals that they should not do anything untoward, and to the international community about how much China takes into account outside pressure," said Nicholas Bequelin, a researcher for the nonprofit group Human Rights Watch.

The government's case includes charges that Liu collected 300 signatures for the manifesto known as Charter 08, a petition with recommendations for constitutional reforms that would make the ruling Communist Party more accountable.

Liu's lawyers say he collected only 60 to 70 signatures. In all, the document attracted 10,000 signers, including academics, writers, lawyers, businesspeople and former party officials.

The manifesto is modeled on the Soviet-era Charter 77 signed by dissidents in what was then Czechoslovakia.

Activists had hoped that officials would release Liu during President Obama's visit to China last month. U.S. officials had given Beijing leaders a list of "cases of concern" that included the case of the well-known scholar, who left a teaching position at Columbia University in 1989 to join the student-led protests in the Chinese capital.

Liu was taken into custody at his Beijing home last December. The move immediately drew international attention, and came just before the 60th anniversary of the United Nations' adoption of the Universal Declaration of Human Rights, a document credited with inspiring the modern human rights movement.

"It's not news that China goes after dissenters and critics, but Liu had been tolerated by the government for so many years," he said. "While he was under surveillance, he was at home writing his articles and meeting with friends, journalists and diplomats.

"He was protected by his international reputation. This is a lesson for everyone. If Liu can end up in jail, no one is safe."